Crankshaft for internal-combustion engines



Jul 18 19 1945. I Q SPECHT 2,378,592

CRANKSHAFTv FOR INTERNAL-COMBUSTION ENGINES Filed Nov. 25, 1940 18 I 4 I i WJW i) Inventor:

Patented June 19, 1945 I CRANKSHAFT FORINTERNAL-COMBUSTION ENGINES Otto Specht, Berlin-Spandau, Germany; vested in the Alien'Property Custodian t Application November 23, 194.0, Serial No. 366346 In-Germany September 7, 1939 6 Claims.

The invention relates to a crankshaft for internal combustion engines'having balance masses for eliminating vibrations pendulously suspended on rollers between raceways, particularly after the manner of a centrifugal pendulum of the bifi1ar isuspension type. With these known devices with centrifugal pendulums, the position of the rollers during the starting periodof the rotation, especially when the device is tuned for damping vibrations of low orders, is no longer corresponding to the geometrical conditions of the pendulum length be- .cause-the' inclinationangle of the raceways is not sufiic'ient'to return the rollers under the action ofthe centrifugal force into the geometrically correct position. This has the consequence that thecenters of the raceways and of the'rollers do notlie on one line, so that an uncontrollable variation ofthe pendulum length and thus of the tuning conditions occurs. A pendulum of thiskind cannot function to full satisfaction betaking into consideration the varying length. These articulation points may be placed on-the center lines of the raceways at'any distance but equally spaced from the respective raceway centers. 1 I

The drawing illustrates diagrammatically embodiments of the invention.

Fig. 1 shows a side elevation of a dampening device according to the invention, and

cause the'different mas elements of the pendulous weightwould have .to swing with different pendulum lengths. The deficiency becomes particularly evident if the pendulum is tuned to low vibration orders, as with such a tuning the angle of inclination within the operative range of the raceways is particularly small owing to the great length of the pendulum, so thatthere is no pos sibility of returning the rollers into the original ,correctpositionagainst the influence of themavoidable friction.

' These disadvantages are eliminated, according to the invention, by connecting the-rollers with guides or links capable of maintaining the pre': scribed pendulum length. This guiding is eflectred in such a way that in any-position of the pendulum the rollers maintain the geometricalpendulum length. When using links, these arepreferably double-armed levers having their fulcrum journalled to the rollers, the free lever ends being articulated on'the one hand to the pendulum weight and on the other to the rotating machine element. The most appropriate articulaltionpoints of the links at the rotating part and .at the swinging weight of the pendulum arrange- .ment are theyraceway centers, which, in each pair of raceways, are at a distance of one pendumm length from the center of the associated roller. If constructional considerations do not permit such an articulation of the links, it is recommended to provide for a pivotal and movable' mounting of both ends of each link at' the rotating part and at the pendulous weight respec .tively, preferably byusing a slotted guide, thus Fig; 2 a section taken along the line IV-IV of Fig. 1. Y

Fig. 3 is explanatory and refers to the device illustrated in Figs. 1 and 2.

Figs. 1 and 2 show a centrifugal bifilar pendulum, e. g., foran internal combustion engine for dampening torsional vibrations in the crank shaft. The device comprises a crank cheek l5 mountedon'the crankshaft (not shown) of the engine so as to rotate, when in operation, in the plane of illustration about an axis located above the illustrated structure. .A weight l'lis suspended from the radially outer end of the crank cheek 1.5 so as to be subjected to centrifugal force when in operation. Cheek l5 and weight I! are joined with each other by means of rollers I and links or levers 3 so as to permit the weight to effect pendulous movements relative to the crank cheek. The crank cheek I5 passes through a radial opening I6 into a transversal recess l8 of the centrifugal weight I! and is provided with projections l9 and 20. These projections l9 and 2|] may be made in one piece with the crank shaft IE or, as illustrated, may consist of separate plates attached-to both sides of the cheek and secured theretoby means of bolts 2|.

' jections or plates, l9 and 20 form outer raceways 4, while inner raceways 5 are provided in the opposed wall of the transverse recess [8 in the centrifugal weight ll. Each pair of race- .ways 4 and 5 is engagedby a roller i which is the other end 1 is articularly connected with the upper part of the centrifugal weight H as at l2.

The function of the roller and lever mechanism will be understood from Fig. 3. The axis of the roller I lies in the center of the double-armed lever 3.' Since the opposite ends of each lever 3 are respectively connected to the pendulum at point l2 and to the crankshaft web at l3, the roller is maintained in a definite position relative the inner and outer arcuat'e raceways 4 and 5,. and therefore each swing of the pendulum will The protake place about the prescribed path determined by said arcuate raceways. If, however, the arms 3 were not provided and the freely mounted roller I were permitted to slide relative to one of the surfaces 4 or 5, the prescribed path of the pendulum swing would be changed, thus changing the damping effect of the pendulum,

According to the present invention, links 3 serve as a cage for roller I. At the point [2 where one end of the link 3 is articulated to the pendulum ll, this point is disposed along a straight line 12a, [2, 2, I3, [222 containing the radii for both arcuate surfaces 4 and 5 when the parts are in normal bold line position as shown in Fig. 3. At the point l3; the other end of link 3 is articulated to the crank cheek- I9, 28' along the above-mentioned. straight line 12a; l2", 2, l3, [2b, said points [2 and I3 beingequidistant from point 2. Thus, it is seen that sliding or scufiing of the roller will be prevented and that the peripheral elements or roller I. will always tangentially engage. the corresponding elements of the arcuate raceway surfaces: 4 and S'When'the pendulum swings.- from normal position,

In bifilar pendulums such as disclosed, each of the pendulum elements swings about a radius or pendulum length equal t0: the distance: between points lZa and 12b, and thereforeeach position of the pendulum is always parallel to the succeeding position. In Fig. 3, the pins. l2 andv 13 are each located from the roller center. 2 a distance less than the pendulum length l-za 21;, consequently, elongated slots. l0. and H mustpbeprovided; The necessary length, of these slots will. diminish according to theproximity oi pins-l1-2 and I3 to: the theoretical centers lzaaand, l12'b. If pins 125 and [3 are located 'at. therespective centers Ila. and no, the: slots need only to be long enough to prevent the pins from carrying any of the loadsupported by roller- L.

Fig. 3' is adiagrammatic. view exaggerating the .movement of the pendulum: IT for the sake of illustration. In operation, the pendulum actually swings back and forth through avery small arc which. is only a fractionof that shown in Fig. 3. The bold line. position of the parts inv this view correspond with the normal. position of the pendulum as shownin- Fig. l, whereas the dotted line position corresponds to a position where the pendulum l1 and: point ill have swung. tothe-left of. the position shown in Fig, l.

l. A.,rot-ar.ydevice for dampening vibrations, in particular in crankshafts of. internal combustion engines; comprising a. rotating member, a weight. suspended from the. radially outer: end of said member so as to be; subjected; toeentrifugal force when in operation, rollers arranged between said member and. said; weight,; and raceways arrangedon said member and! said; weight and engaging said rollers. topermit; said-weight pendulous movements relative to saidxmember,

and a. guiding mechanism connecting; said; member with said. weight. and engaging said rollers for constrainedly guiding, saidi rollers to main-. tain: a constant geometrical pendulum. length in every position or said weight relative'toi said member, said mechanism having lostrmotionbetween said rollers; onxthe. one hand, and; said member and Weight, on the o-therhandinga diweight suspended from the radially outer end of said member so as to subjected to centrifugal force when in operation, rollers arranged between said member and said weight, and arcuate raceways arranged on said member and said weight and engaging said rollers to permit said weight pendulous movements relative to said member, twoguiding links .journall'ect at both axial sides respectively of each roller, and means for respectively connecting each of said links with said roller, member, and said Weight at points lying in a straight: line containing the common radii of said raceways, whereby said roller is guided in a constrained dependence upon movements of said weight relative to said member, said link connections between said link on one hand, and said weight and member on the other comprising lost motion in a direction perpendicular to the rolling direction of said rollers on said raceways.

3. A rotary device for dampening vibrations, in 1 levers having the ends thereof respectively-io.ur-

nailed to saidv weight and to. said; member about an axis coaxial: with the. radii: of: said racewa-ys when the parts. are in normal position,,said roller being pivotally connected to the. center of said lever. v

4-. A rotary device-for dampening. vibrations, in

particular in crankshafts ofinternals combustion engines, comprising a rotatingimember, aweight suspended from the. radially outer end of said .member so as to'be subjected to centrifugal force rection. perpendicular to. the rollingt direction of I saidrollers on. saidraceways.

2. A rotary device for-dampening: vibrations, I

in particular in crankshafts of. internal combustion. engines, comprisingta rotating member, a,

when in operation, rollers: arranged betweerr said member and said. weight nand curved raceways arranged on said member and s-aidweight and engaging said rollers. to permit'said', weight. pendulous movements relative tosaid member, and two doublearm levers arranged at. both axial sides respectively: of eachroller, means i for rotatably connecting thece'nter or. each of. said. levers to said roller, and means for 'pivotallyconnecting the ends of each of: saidalevers withisaid: member and said weight respectively at. points equally .spaced from the roller centers, said latter: points lying in aline coaxial withthe radii of. said; race.- ways, and saidpivotal connections having lost .motion. in the direction" of the: connecting. line containing said-points.

5. A rotary device for dampeningrvibrationain particular in crankshafts of.'internal.combustion engines, comprising a. rotating member, a. weight suspended from the radially; outer end of said member so asto be subjectedxto centnifngalzforce y when in operation, rollers; arrangedibretweenisaid member and said weight, andaraceways'arranged on said member and; said weights and. engaging said rollers to permit said weight pendulous movements relative to: said. member, and a guidi ng mechanism for confiningr'themolling movements of said rollers. relative'to said: membmrand said weight. so, asv to: maintain a constant. geotmetrical. pendulum length in every position of saidweightrelative to said membensaidnrechanism being linked tosaid membenand to: said raceways arranged on said member and said weight, said raceways engaging said roller to permit pendulous movement of said weight relative to said member, and means carried by said roller and operatively connected to said member and to said weight for preventing slippage of said roller upon said raceways in every position of said weight relative to said member.

O'I'I'O SPECHT. 

